Rechargeable batteries are known to fail unexpectedly via short-circuiting through metallic dendrites that grow between electrodes upon recharging. This phenomenon triggers a series of events that begin with overheating, eventually followed by the thermal decomposition and ultimately the ignition of the organic solvents used in such devices. This flaw has become a major safety issue in the operation of the recently introduced larger passenger aircraft.
Many efforts have focused on exploring the effects of chemical composition and morphology of various electrode materials (see J. M Tarascon, M. A., Issues and challenges facing rechargeable lithium batteries. Nature, 2001 414: p. 359-367; Armand, M. and J. M. Tarascon, Building better batteries. Nature, 2008. 451 (7179): p. 652-657) and the nature of solvents and electrolytes (see Xu, K., Nonaqueous liquid electrolytes for lithium-based rechargeable batteries. Chem Rev, 2004. 104 (10): p. 4303-417) on the energy density and lifetime of batteries. However, ultimate battery performance is still limited by capacity decay and failure due to short-circuiting via dendrite formation. Lithium is used in lithium battery electrodes, whose energy density (3862 mAh/g) is more than 10 times larger than graphite (372 mAh/g). On the other hand, lithium is more prone to grow dendrites relative to graphite, since lithium deposition is dominant over lithium intercalation (see Daniel, C., Materials and Processing for Lithium-Ion Batteries. JOM, 2008. 60).
Researchers have tried to prevent the growth of dendritic microstructures using various techniques, which are still unsuccessful. On the experimental side, several studies have tracked the influence of control parameters such as current density (see F. Orsini, A.D.P., B. Beaudoin, J. M. Tarascon, M. Trentin, N. Langenhuisen, E. D. Beer, P. Notten, In Situ Scanning Electron Microscopy (SEM) observation of interfaces with plastic lithium batteries. Journal of power sources, 1998. 76: p. 19-29; Graciela Gonzalez, M. R., and Elisabeth Chassaing, Transition between two dendritic growth mechanisms in electrodeposition. Physical Review E, 2008. 78 (011601)), geometry (see Monroe, C. and J. Newman, The effect of interfacial deformation on electrodeposition kinetics. Journal of the Electrochemical Society, 2004. 151 (6): p. A880-A886; Liu, X. H., et al., Lithium fiber growth on the anode in a nanowire lithium ion battery during charging. Applied Physics Letters, 2011. 98 (18)), solvent and electrolyte chemical composition (see Crowther, O. and A. C. West, Effect of electrolyte composition on lithium dendrite growth. Journal of the Electrochemical Society, 2008. 155 (11): p. A806-A811; Howlett, P. C., D. R. MacFarlane, and A. F. Hollenkamp, A sealed optical cell for the study of lithium-electrode electrolyte interfaces. Journal of Power Sources, 2003. 114 (2): p. 277-284; Schweikert, N., et al., Suppressed lithium dendrite growth in lithium batteries using ionic liquid electrolytes: Investigation by electrochemical impedance spectroscopy, scanning electron microscopy, and in situ 7Li nuclear magnetic resonance spectroscopy. Journal of Power Sources, 2013. 228 (0): p. 237-243) and electrolyte concentration (see Brissot, C., et al., In situ concentration cartography in the neighborhood of dendrites growing in lithium/polymer-electrolyte/lithium cells. Journal of the Electrochemical Society, 1999. 146 (12): p. 4393-4400; Brissot, C., et al., Concentration measurements in lithium/polymer-electrolyte/lithium cells during cycling. Journal of Power Sources, 2001. 94 (2): p. 212-218) on dendrite formation.
Methods that have been developed to slow down dendrite formation include the use of powdered electrodes (see Kim, W. S. and W. Y. Yoon, Observation of dendritic growth on Li powder anode using optical cell. Electrochimica Acta, 2004. 50 (2-3): p. 541-545), the application of successive bipolar charge pulses (see Chen, L. L., Xue Li Zhao, Qiang Cai, Wen Bin Jiang, Zhi Yu Bipolar Pulse current method for inhibiting the formation and lithium dendrites. Acta Phys. Chim. Sin, 2006. 22 (9): p. 1155-1158), and covering lithium electrodes with adhesive lamellar block copolymers (see Stone, G. M., et al., Resolution of the Modulus versus Adhesion Dilemma in Solid Polymer Electrolytes for Rechargeable Lithium Metal Batteries. Journal of the Electrochemical Society, 2012. 159 (3): p. A222-A227).
The dynamics of dendrite growth also has been characterized to some extent. Studies gave considered evolution time (see Rosso, M., et al., Onset of dendritic growth in lithium/polymer cells. Journal of Power Sources, 2001. 97-8: p. 804-806), growth rate (see Brissot, C., et al., In situ study of dendritic growth in lithium/PEO-salt/lithium cells. Electrochimica Acta, 1998. 43 (10-11): p. 1569-1574) and electrolyte convection see Fleury, V., J. N. Chazalviel, and M. Rosso, Theory and Experimental-Evidence of Electroconvection around Electrochemical Deposits. Physical Review Letters, 1992. 68 (16): p. 2492-2495).
On the theoretical side, the few idealistic schemes have been developed to account for lithium dendrite growth have multiple deficiencies, such as dendrite shape and one dimensional cell geometry (see Chazalviel, J. N., Electrochemical Aspects of the Generation of Ramified Metallic Electrodeposits. Physical Review A, 1990. 42 (12): p. 7355-7367; Monroe, C. and J. Newman, Dendrite growth in lithium/polymer systems—A propagation model for liquid electrolytes under galvanostatic conditions. Journal of the Electrochemical Society, 2003. 150 (10): p. A1377-A1384). This has been confirmed by experimental studies on electrochemical deposition of zinc and copper (see Sagues, F., M. Q. Lopez-Salvans, and J. Claret, Growth and forms in quasi-two-dimensional electrocrystallization. Physics Reports-Review Section of Physics Letters, 2000. 337 (1-2): p. 97-115). Nonetheless, the dendrite morphology evolution mechanism is not yet understood. The microstructure study is experimentally hard and the SEM imaging of dendrites is not usually practical since the dendrites are very fragile and disassembling the cell and exposure of lithium metal to open atmosphere will not provide accurate results, for example because lithium reacts with oxygen and water vapor in the atmosphere.
Other experimental approaches for observing dendrites have been unsuccessful as well (see Brissot, C., et al., Dendritic growth mechanisms in lithium/polymer cells. Journal of Power Sources, 1999. 81: p. 925-929).
There is a need for systems and methods that allow more accurate observation of dendrite formation dynamics in more realistic device similar to current batteries.